The invention concerns geared motors with a flat construction according to the generic parts of the main claims.
The generic measures for electrical driving devices intended in particular for the adjustment of windows in motor vehicles are known from DE 22 10 243 B2. On one side they have an intermediate wall with an electric motor, the disc armature of which rotates in a flat air gap, and opposite to it has a planetary gear drive in the form of a planetary gear arrangement with a cable drum. The mounting of the armature and of the gear drive takes place in the intermediate wall as well as in the hat-shaped external walls serving as bearing supports, the perimeter of which are bolted to one another and a supporting component via a reinforced edge of the intermediate wall. A disadvantage of this driving device is first of all the high manufacturing cost and the relatively low efficiency of the planetary gear drive as well as the complicated shape of the external walls that are to be dimensioned so that to be a bearing support.
From DE 2 96 22 874 U1 a geared motor with disc armature and planetary gear drive is known, that has the peculiarities that on the circuit board for the control electronics it carries also flat coils for the rotor, while the gear drive can be constructed also as an eccentric drive with a centrally mounted eccentric gear for continuous engagement in the adjacently situated inner gears of hollow wheels. Such a gear drive places also additional requirements on the manufacturing and assembly tolerances, and due to the continuous eccentricity of the load transfer has an even worse gear efficiency even at a moderate reduction ratio.
Therefore the object of the invention is to improve geared motors with flat construction of the type mentioned in the introduction, that are suitable for installation particularly in flat surroundings, like narrow hollow wall spaces in light constructions, but also in functional parts like hollow walls of housings and particularly in hollow spaces of relatively slowly rotating or rotatably adjustable devices, for advertising purposes (rotary displays), for entertainment electronics (rotary tables), for furniture to sit or lie on (recline and level adjustment) or for laboratory purposes (sample turret, agitator), so that they would be characterised by a simpler construction and better kinetic ratios.
This objective is achieved by the essential features of the invention stated in the main claims.
According to them the motor with the flat construction is provided rotationally fixed on one side of an approximately H-shaped housing/base body from a yoke plate with continuous rim flanges. This rim is constructed by becoming thicker towards the periphery of the central disc, by extending on both sides of the edge of the central disc as an axially parallel sleeve having a very thick wall, the axial length of which is approximately the same as the axial thickness of the geared motor, so that practically plane housing covers can be used. Thus the solid collar-shaped or sleeve-shaped rim, that is continuous around the central yoke plate on the periphery of the base body and is more than a mere thickening of the edge, acts directly as an annular, therefore almost hollow-cylindrical housing wall that is axially short when compared with the diameter. The flat housing covers, that are mounted on the face of the rim serve as axial stops for the rotating parts and, if necessary, are appropriately reinforced in the centre, as bearing shield, for example, for the driven stub shaft; thus they complement the construction of the disc geared motor according to the invention that has essentially the form of a circular disc and is very flat in comparison with the diameter.
The drive of the gear drive is a commercially available electric motor with a disc-shaped rotor geometry. Although due to the fact that it has the shape of a disc, and not that of a ring or roller, the rotor rotates relatively slowly, but it is characterised by a high torque in conjunction with a large flywheel mass. Such a motor can be used with a disc rotor, but also as a rotor axially shortened to a disc with windings using the electromagnetic principle.
Such a motor is rotatably joined through a central opening in the central disc of the housing/base body with a reducing gear drive also having a flat construction. Part of this gear drive is a driven ring that rotates coaxially along the inner periphery of the rim, which driven ring can be, in turn, part of a flat bell dome with a driven stub shaft accommodating a driven pinion that is coaxial with the motor. However, instead of this or in addition to the bell stub shaft, on its jacket surface the driven ring can be constructed as a belt pulley, a sprocket or as a cable drum depending from the transmission means used. In that case, in that half of the rim that surrounds the gear drive the driven ring is accessible from the outside through openings in the housing for the transmission means, perhaps for a belt.
Finally, in the region of its periphery the driven ring can be fitted with at least one ferromagnetic part, preferably with a permanent magnet. Due to the magnetic interaction, its [the permanent magnet""s] movement of the permanent around the housing of the gear drive carries with it a complementarily fitted rotatable element outside of the housing of the gear drive. Such a contact-free coupling used to transmit force makes the use of a housing hermetically sealed against environmental influences for the entire unit of the disc-shaped geared motor feasible.
In the centre of the gear drive the motor shaft engaging the gear drive carries a drive element, and in an annular space between the drive element and the driven ring at least one transmission element rotates. Consequently, using a very simple construction a very large reduction with very favourable kinetic ratios is delivered by a wave drive, whereby its eccentric, so called wave generator, is rotated as the driven element rotated by the motor in the elastically deformable hub of the sole transmission element, the so called tappet wheel, that can be deformed on the periphery; this is described in detail in DE 197 98 310 A1 or is known form the publication xe2x80x9cThe harmonic drive electromechanical actuatorxe2x80x9d by V. O""Gorman in Control Engineering (December 1964, pp. 69-72) as a cylindrical drive acting as a highly dynamic synchronous motor or like an efficient step motor.
The spur gearing of this transmission element, that rotates while being radially deformed, is meshed with the internal teeth on the driven ring and simultaneously also axially in addition to the driven ring with the internal teeth of somewhat greater number on a support ring fixed on the housing, coaxially protruding rib-shaped from the rim or collar-like from the yoke disc. This support ring with the internal teeth can be integrally produced with the housing. However, from the point of manufacturing technology, an accurate roundness can be easier achieved when the ring is manufactured separately and is concentrically installed in the housing.
Instead of the wave drive a wobble wheel drive may be used on that side of the yoke disc which is averted from the motor, especially when no extreme reduction is required.
There are further possibilities of application and advantageous possibilities of manufacturing the compact disc-shaped geared motor by integrating the driving element in the axially flat gear drive with the rotor of the driving motor, what has manufacturing advantages. This integration results in an even simpler assembly of the geared motor with reduced requirements on the part logistics when a support disc for carrying the conductor tracks of a disc armature rotor is integrally produced by plastic injection moulding with the shaft of the gear drive. The conductor track carrier for the electro-motoric function of the rotor connected on the slip ring against a stator with preferably permanent magnets can be appropriately applied to the disc using the MID technology, that is explained in detail in our German patent application 19840665 of May 9, 1998, to which total reference is made herein to avoid repetitions, i.e. by using covering or lamination, in particular by additive or semi-additive chemical metallising methods.